The present application corresponds to French application Serial No. 00 13688 filed Oct. 25, 2000, the disclosure of which is incorporated herein by reference.
The present invention relates to the field of bituminous sealing products, and has for its object a process for the production of a bituminous sealing sheet or membrane, an installation for practicing the process, a sheet or membrane obtained by this process, as well as a sealing system for roofs comprising such sheets or membranes.
The present bituminous sheets or membranes are generally produced by drawing a coating support (for example a fibrous or filamentary armature) through a coating line comprising at least one, and preferably several, coating stations each formed with a vat containing bitumen or a mixture or a composition based on bitumen in liquid form, in which is immersed a rotatable printing or coating roller over which said armature passes lengthwise.
Each coating roller thus applies a layer of bitumen on the underside of the armature whilst liquid bitumen is also poured on the upper surface by means of vats or pouring lips, the bitumen being immediately after application and before cooling forcibly impregnated into the armature by means for example of two opposite calender rolls determining the thickness of the layers of bitumen by scraping off the surplus and leaving the surfaces of said armature impregnated and coated.
After cooling and solidification of the layers of bitumen, said impregnated and/or coated armature is cut into segments of predetermined length, forming as many sheets or individual membranes, generally rolled up in rolls for their storage, transport and handling, and unrolled at the work site before their installation.
These bituminous sheets are applied to supports to be covered and laterally welded to each other by heating of their undersurfaces with a torch to render the corresponding layer of bitumen fluid.
However, this mode of securement is troublesome in the presence of a flame at a work site is always an important risk factor.
Moreover, numerous supports or constituents to be sealed are more or less flammable or do not resist the heat produced by a torch.
To seek to overcome these drawbacks, there have been proposed sheets and membranes with self-adhesive undersurfaces over all their surface, for example by application of a cold adhesive bitumen. Nevertheless, this surface adherence can give rise to too great and intimate contact between the support and these sheets or membranes, which does not permit distributing tension nor relative movements between them, or even a diffusion of the possible gas pockets present on the undersurfaces.
Moreover, all of the undersurface must be covered by an expensive peelable protective sheet, whose removal can prove to be troublesome at the work site and generate a great deal of waste. Moreover, a good quality of securement can be obtained only during the first attempt at securement, the level of sealing obtained at the overlapping edges between sheets and adjacent membranes that partially overlap in limited regions, not being comparable to that obtained by hot welding and the use of a large quantity of cold self-adherent bitumen, which raises the cost.
To seek to overcome the limitations mentioned above, different improved solutions have been proposed, namely, auto-adhesive sealing sheets having at their edge a thermal weldable strip (see particularly: EP0 352 394), sealing sheets having on their undersurface only spaced strips of self-adhesive bitumen or else sealing sheets fixed mechanically along one of their edges (the opposite edge of the adjacent sheets covering these securements with a thermal weldable strip to ensure sealing).
However, the first and second mentioned solutions imply a return to the use of torches and the second solution gives rise to inequalities of the surface because of the extra thickness at the strips of self-sticking bitumen provided on the undersurface and do not confer sufficient mechanical resistance to tearing apart, because of the small adherent surfaces connected to a securement by simple deposit of said strips of self-adhesive bitumen on the lower layer of bitumen.
A problem faced by the present invention thus consists in providing a process for the production of a sealing sheet or membrane having on at least one of its surfaces at least one strip of bitumen with different properties, without increasing the thickness or with a decreased thickness and having intimate securement with said membrane or sheet.
To this end, the present invention has for its principal object a process for the production of a bituminous sealing sheet or membrane comprising an armature impregnated and/or coated with at least one bitumen, or at least one bitumen base mixture, provided on at least one of its surfaces and having at least one region in the shape of a strip or portion of a strip of bitumen, or of a bitumen base mixture, different from said bitumen or mixture applied in the first instance, on at least one of its surfaces, which process is characterized in that it consists in producing a strip of armature impregnated and/or coated except for at least one region in the form of a strip or of a portion of a strip on at least one of its surfaces, having a bitumen thickness less than or having no bitumen application, relative to the level of said at least one strip or strip portion, over a controlled thickness, a bitumen or a bitumen base mixture different from that of or those previously applied and, finally, after cooling and solidification or the bitumens or bitumen base mixtures, providing the resulting sealing sheet or membrane in the desired form.
Preferably, all of the operations of treatment mentioned above are carried out in a known manner by continuous lengthwise movement of the armature in a suitable installation or coating line comprising at least two coating stations.